Study gives new view on how ion-channel activity is regulated.
A common protein plays a different role than previously thought in the opening and closing of channels that let ions flow in and out of our cells, researchers at Johns Hopkins report. Those channels are critical to life, as having the right concentrations of sodium and calcium ions in cells enables healthy brain communication, heart contraction and many other processes.
The new study reveals that a form of calmodulin long thought to be dormant actually opens these channels wide. The finding is likely to bring new insight into disorders caused by faulty control of these channels, such as cardiac arrhythmias, epilepsy and Parkinson’s disease, the researchers say. The study is published in the journal Cell.
In the currently accepted model calmodulin can do little until it binds to calcium, which changes its shape and snaps it into action. The activated calmodulin can then bind to a specialized control lever inside calcium and sodium channels, which closes the channels.
The new study revises this viewpoint by devising ways to deliver surges of calcium-free calmodulin to channels. In so doing, it can be seen that calcium-free calmodulin is in no way dormant, but instead markedly boosts the opening of calcium and sodium channels to begin with.
When calcium binds to the resident calcium-free calmodulin on channels, this initial enhancement dissipates. The two forms of calmodulin are both powerful, each imposing opposing actions that together maintain exquisite control, akin to the ‘yin-yang’ balance in Chinese philosophy.
This insight into how the calmodulin-controlled lever works could ultimately help in finding treatments for a plethora of conditions that stem from faulty ion channels. The team summise that a presumably dormant form of a common protein turns out to strongly regulate the opening and closing of calcium and sodium channels.
The discovery could be central to treating channel-related diseases such as cardiac arrhythmias, epilepsy and Parkinson’s.
Source: The Johns Hopkins University